Accounting for Commercial Vehicles in Urban Transportation Models

Magnitude and Distribution

2.0 Types of Commercial Vehicles

This section presents a detailed definition of the term "commercial vehicle" for the purposes of this study and summarizes the commercial vehicle categories established for this review. This section also includes definitions of commercial vehicle categories that are contained in some of the data sources being analyzed.

2.1 Definitions

"Commercial vehicles" include a broad range of vehicle types that are used for commercial, rental, educational, and government services. Examples of the uses for such vehicles include: transportation of persons, package and mail delivery, urban freight distribution, utilities, trades and services, landscaping services, outside sales, product delivery, vehicle rental, transportation of school children, construction activity, and paratransit services.

Commercial vehicles demonstrate temporal and geographic distributions which differ from those of personal vehicles. In traditional transportation planning studies estimates of household vehicle trips are factored to correct for underreporting and underpredicting of commercial vehicle trips in traditional transportation planning data sources. While traditional travel models are adequate for some basic analyses, improved methods for estimating commercial vehicle trips would provide capabilities for more accurate analysis of additional transportation planning functions and for the analysis of a wider range of transportation policies.

The overall objective of this task is to develop an improved understanding of the magnitude and the spatial and temporal distribution of commercial vehicle trips within urban areas, other than those trips that represent intercity freight movements. A better understanding of commercial vehicle travel will improve the accuracy of travel demand forecasting procedures, thereby leading to more effective means of managing transportation facilities. Equally important, improved estimates of commercial vehicle travel also will enable transportation planners to make better estimates of congestion and environmental impacts, including mobile source emissions and transportation air quality.

"Commercial Vehicle" Definition for This Study

Commercial vehicle trips are primarily organized into three groups, based on what is being carried and the economic, demographic, and land use factors influencing the magnitude and distribution of commercial vehicle trips in a metropolitan area. The three groups are:

1. Movement of people;
2. Movement of goods; and
3. Services.

The movement of people category includes school buses, shuttle services, rental cars, taxis, and paratransit vehicles. In general, growth of this category of commercial vehicles tends to depend on the growth of population and employment in a metropolitan area.

The movement of goods category includes mail delivery, trash collection, warehouse delivery, parcel pickup and delivery, and construction vehicles. In recent years, much attention has been paid to this category of commercial vehicle trips. In metropolitan areas, goods movement trips, similar to longer-haul freight movements, are becoming a larger share of the total on-road vehicle load.

Finally the services category includes household/building services such as plumbers and cleaning services as well as public safety, utility maintenance, and retail support functions. Due to the shift in the United States from a manufacturing-oriented economy to a service-oriented economy, the number of service-related commercial vehicle trips is growing faster than the number of trips for other purposes.

The objective is to account for all three categories of commercial vehicles. Many vehicles registered as commercial vehicles can be defined as commercial vehicles based on the above definitions, but other vehicles falling into these categories are registered as private vehicles. For example, a realtor may register his automobile as a private vehicle but often use it for business purposes. On the other hand, many vehicles are registered as commercial but also are used for personal non-commercial purposes. Any vehicle used for commercial purposes is considered in this study as a commercial vehicle, regardless of how it is registered. It should be noted that vehicle registration rules and practices with respect to commercial vehicles differ by state, further complicating the separate identification of commercial vehicle usage patterns.

Vehicle Registration Definition

The contents of vehicle registration databases vary from state to state as well as by the department collecting the data. State departments of revenue collect vehicle registration data for tax purposes. These databases typically include data related to how the vehicle is taxed and how registration fees are determined, e.g., vehicle age, engine displacement and/or weight class, as well as transaction data. State departments of motor vehicles (DMV) collect vehicle data for safety and/or registration purposes. These databases tend to include more activity information, such as odometer readings, violations, and county of residence. Vehicle data also may be collected at the county or municipality level and consolidated at the state level by a state public service agency. Even within a state, county/municipality data records typically are not uniform.

Vehicle classification counts and commercial vehicle surveys often are used to develop the fleet mix information that is required to carry out air quality analyses. Two additional databases, vehicle registration and emissions inspection and maintenance (I/M) program databases, also contain vehicle information and, on occasion, are used to develop information on the magnitude of commercial vehicle travel.

Freight Analysis Framework/Highway Performance Monitoring System Definition

The Freight Analysis Framework (FAF) is a policy and systems methodology developed by the Federal Highway Administration (FHWA) to estimate freight flows on the nation's highways and other transportation infrastructure. This analysis tool seeks to aid in understanding the geographic relationships between local flows and the nation's overall transportation system. As part of the methodology, information has been developed on truck flows carrying intercity freight, as well as truck volumes that serve purposes other than carrying intercity freight.

The total truck volumes currently used in the FAF are primarily from the Highway Performance Monitoring System (HPMS). The HPMS is a national-level highway information system maintained by FHWA that includes data on the extent, condition, performance, use, and operating characteristics of the nation's highways. The HPMS contains administrative and system information on all public roads, some physical characteristics of arterial and collector functional systems and more detailed characteristics on a sample of different facility types. The sampled data is developed so that it may be expanded to represent all public roads. The FAF provides detail on freight trucks and on non-freight trucks using the FHWA vehicle classification count determination. The total truck volumes used in the FAF can only be compared to commercial vehicles in this study once they have been converted into various vehicles types (autos, buses, trucks, etc.).

Commercial Vehicle Survey Definition

Commercial vehicle survey data was received and processed for the Atlanta, Denver, Detroit and Greensboro/High Point/Winston-Salem metropolitan areas. Each survey was conducted independently, mainly for the purposes of refining or developing a "truck" model (as opposed to a "commercial vehicle" model). The definition of "truck" varies among these surveys. As discussed above, commercial vehicle trips constitute a much broader category of total metropolitan area travel than truck trips.

Each survey was generally performed in two steps. In the first step, a random sample of firms was contacted to participate in the survey and to report information about all of their commercial vehicles. The list of firms from which the sample was generated typically represented all firms known to operate commercial vehicles (usually trucks). In the second step of the survey, the drivers of participant vehicles were given a travel log and instructions on how to record all trips taken during the survey day.

It is important to note that in some surveys, certain types of vehicle were excluded. For example, the Denver commercial vehicle survey excluded auto and truck rental businesses, as well as police, fire, taxi, and U.S. Postal Service operations.

2.2 Categories

Categories for This Study

In the literature review¹ commercial vehicles were grouped into 13 categories, according to the type of service (fixed-route, demand-responsive, or other) and by the type of load (people, goods, services, or other). The literature review was performed for each of these categories separately and summarized.

In this task, while collecting and analyzing data from different sources, we reevaluated these 13 categories and made several changes. It was realized that category 6, "Package and Mail Delivery," and category 8, "Product and Package Delivery," are similar in characteristics and trip patterns. These two categories were combined into one category, "Package, Product, and Mail Delivery." It also was evident from the California DMV data that Federal, state, city, and local government vehicles comprise a significant number of commercial vehicles and that these vehicles should be in a separate category. This category is named as the "Public Service" category. In addition, "garbage trucks, meter readers, maintenance vehicles" and "electricians, plumbers" include similar types of vehicles, and their trip patterns also are similar. Thus, we combined these two categories into a new category named "Utility Vehicles." The "Public Safety" category also is renamed as "Safety Vehicles," since this category includes both public and private vehicles. Finally we introduced a new category called "Business and Personal Services," which includes the previous "Outside Sales" vehicles.

To summarize, two pairs of original categories were combined into single categories while one new category was created, resulting in a total of 12 categories. The original and new categories are shown in Table 2.1.

Source: Cambridge Systematics, Inc.

Other Categorizations

Various other sources of commercial vehicle information use different categorization schemes. These are summarized below.

Vehicle Inventory and Use Survey Categories

The Vehicle Inventory and Use Survey (VIUS) provides data on the physical and operational characteristics of the nation's truck population. This survey is conducted every five years as part of the economic census. Title 13 of the United States Code (Sections 131, 191, and 224) directs the Census Bureau to take the economic census every five years, in years ending in 2 and 7.

VIUS data can be extracted by body type, products carried, and major use. The body type is defined as the type of body that is permanently attached to the power unit. The body type in the VIUS was cross tabulated with the "product carried" and "major use" categories in the VIUS database. Based on the results of this cross tabulation, each "product carried" category and "major use" category was assigned to the 12 categories given in Table 2.1. Table 2.2 shows the matching of the body type to the 12 categories that correspond to the "products carried" and "major use" categories in the VIUS. When the categorization based on "product carried" and "major use" categories conflicted, the "major use" category was selected for use in this study.

Source: Cambridge Systematics, Inc.

In addition, the following vehicle sizes also are available. The vehicle size is determined by the average weight (defined as empty weight of the vehicle plus the average weight of the load carried):

• Light - Average weight is 10,000 pounds or less;
• Medium - Average weight between 10,001 pounds and 19,500 pounds;
• Light-Heavy - Average weight between 19,501 pounds and 26,000 pounds; and
• Heavy-Heavy - Average weight greater than 26,000 pounds.

Vehicle Registration Categories

State registration databases often, but not always, identify whether or not the vehicle is used for commercial purposes. Data typically are available on vehicle weight classes, but not service use. Many states' data do not include odometer readings. Some state databases could be used to infer the type of service use (as was done in California by the California Energy Commission), based on vehicle make/model, weight class, owner, and possibly other data. However, this requires a considerable amount of data processing and may need to be done by the agency owning the data due to privacy concerns associated with releasing detailed data on ownership. For example, the California Energy Commission reportedly has been working in cooperation with other California state agencies for more than five years in cleaning, organizing, and analyzing their state vehicle data. They categorized vehicles into two main groups:

1. Light Vehicles; and
2. Medium and Heavy Vehicles.

The light duty vehicles are categorized by body type and use categories, as shown in Table 2.3. Medium and heavy duty vehicles are categorized by body type only, as shown in Table 2.4.

Source: California Department of Motor Vehicles registration data processed by the California Energy Commission.

Source: California Department of Motor Vehicles registration data processed by the California Energy Commission.

Freight Analysis Framework/Highway Performance Monitoring System Categories

Vehicle classification counts are required to support the truck percentages submitted as part of the HPMS. The HPMS truck percentages, as applied to the HPMS Average Annualized Daily Traffic (AADT) information, provide the values for the Average Annualized Truck Traffic (AADTT) volumes used for 23 states in the FAF.²

For the remaining states the FAF uses the state's traffic count database, which is more expansive than the required HPMS data, and the HPMS LRSKEY (Linear Referencing System Key) to directly map truck volumes collected as part of a vehicle classification program to the FAF network. The FAF also includes the development of an 'intercity' freight truck trip table. This table was assigned to the FAF network. The resulting FAF truck volumes were subtracted from the AADTT total truck counts to produce 'Non-freight' truck volumes for links on the FAF network.

The definition of trucks, as used in traffic counting programs in support of pavement design, the HPMS, and the FAF, excludes four-tire, two-axle vehicles, including pickup trucks, panel trucks and vans, ambulances and many other vehicles that are commonly considered as commercial vehicles. It also excludes all passenger cars. A significant number of commercial vehicles are passenger cars or four-tire trucks. The vehicle classification counts, and the datasets derived from these vehicle counts, can provide information about the larger commercial vehicles, but can provide no information on four-tire commercial vehicles.

Commercial Vehicle Survey Categories

Commercial vehicle categories varied among the surveys examined as part of this project. Generally, vehicles were categorized as 'light duty,' 'medium duty,' or 'heavy duty.' In some cases, the 'light duty' category was further subdivided into autos and pickups. The survey data typically contained some information on the body type of the vehicle and in some cases including the make and year of the vehicle.

Data gathered in the surveys from the vehicle trip logs generally gave a better insight to the commercial vehicle type than the data gathered about the vehicle itself. For example that a vehicle is known to be a minivan does not provide enough information to categorize it into one of the commercial vehicle type categories, but knowing that the vehicle's cargo was 'tools' and that the purpose of the trip was 'service call' and the destination of the trip was 'residential' indicates that the vehicle should be categorized as a utility vehicle.

While each survey is unique, there is commonality among them, with each survey asking the type of cargo the vehicle was transporting (Cargo), the land use of the destination of the trip (Land Use), and the purpose of the trip (Purpose). It is from these three primary questions that each trip was categorized into one of the commercial vehicle groups. In some cases, additional survey data could be used to determine the vehicle category.

Footnotes

1. Accounting for Commercial Vehicles in Urban Transportation Models, Task 2, Literature Review, prepared for FHWA by Cambridge Systematics. January 2003. http://www.fhwa.dot.gov/planning/tmip/publications/other_reports/commercial_vehicles_transportation/

2. Battelle, Freight Analysis Framework Highway Capacity Analysis: Draft Methodology Report, U.S. Department of Transportation, Office of Freight Management and Operations, Washington, D.C., April 18, 2002, Table 4.1.